The use of airbags in suspension systems for swing-arm type motorcycle suspension systems, particularly Harley Davidson SOFTAIL® motorcycles is known in the prior art. The Harley Davidson SOFTAIL® motorcycle suspension system uses a swingarm that is pivotally attached to the rear frame or main frame side plates of the motorcycle. This allows the rear wheel assembly to move independently from the frame about a singular pivot point. The swingarm rotates about a pivot and allows the wheel to move in an arcuate motion. The swingarm has a pair of wheel mounts that are positioned and spaced to mount a wheel assembly and to provide proper orientation and location for the wheel relative to the motorcycle. The swingarm has a pair of supports at each wheel mount, each pair are positioned in a plane and radiate from the wheel mount to a support member that connects the pair of supports in a planar like orientation.
Transverse bars, or cross members link each of the wheel mounts in an upper location and a lower location providing proper spacing and structural rigidity for the swingarm. At an intermediate position, positioned between the upper and lower cross members, an additional transverse bar or cross member links each wheel mount. The intermediate cross member is tubular, and provides an axis for the swingarm to rotate about. Each of the support members has a hole that coincides with the tubular shaped cross member, providing a through-hole into which pivot bolts are inserted. Each support member is positioned adjacent to, and located inside, the frame and is therefore hidden by the main frame struts, giving the illusion of a motorcycle having no visible suspension system.
The standard or stock SOFTAIL® motorcycle uses a suspension system that incorporates two shock absorbers that are positioned in a parallel relationship to each other and are orientated so the longitudinal axis of the shock absorbers is parallel to the direction of travel of the motorcycle. One end of each of the shock absorbers is attached to the main frame. The other end of each of the shock absorbers is connected to a member that extends forward from the lower cross member of the swingarm. The main frame of the motorcycle hides the shock mounts from view, maintaining the appearance of the SOFTAIL® motorcycle.
Motorcycle airbag rear suspensions have been described in U.S. Pat. No. 6,003,628 (Dec. 21, 1999, herein after the '628 patent), U.S. Pat. No. 6,357,546 (Mar. 19, 2002, hereinafter the '546 patent), and U.S. Pat. No. 6,668,960 (Dec. 30, 2003, herein after the '960 patent), which are hereby incorporated by reference. The '628 and '546 patents are specifically designed for the Harley-Davidson SOFTAIL® rear suspension system. As a result of design constraints imposed by the desire to conceal the rear suspension mechanism, the SOFTAIL® suspension system utilizes an unusual spring and shock absorber arrangement wherein a pair of coil-over shocks are positioned under the frame in front of the swingarm. Unlike the shock absorber assemblies of virtually all other motorcycles, which compress when the swingarm rises, the SOFTAIL® coil-over shock units extend when the swingarm rises.
As a result of the design, airbag devices are not readily compatible with the SOFTAIL® suspension system. Accordingly, an essential element of the '628 patent is an elaborate sliding house mechanism that translates the extending or pulling motion of the SOFTAIL® suspension into a compressing or pushing motion. In contrast, the airbag component of the instant invention is positioned above the pivot point of the swingarm where it is properly situated to be compressed in response to a rising swingarm.
The '546 patent also features a complicated device to translate the extending or pulling motion of the SOFTAIL® suspension to a compressing motion for use with an airbag device. In this case, the invention comprises a pair of pivotally connected plates that share a common pivot axis with the stock SOFTAIL® swingarm and main frame. The lower section of one plate connects to a shock absorber mounted in the conventional SOFTAIL® shock location. The upper part of the pivoting plates accept an airbag, essentially extending the SOFTAIL® suspension above the swingarm frame axis to resemble a more modern swingarm suspension system.
The main problem with the '546 design is the inherent complexity of the added pivot mechanism. The system compresses the airbag in an arc using a bag bracket. The system also does not readily accept different types and sizes of airbags. The system is a scissor type mechanism, which requires more bearing and service areas that could prematurely wear, causing added drag and creating slow or rough action of the swingarm during compression of the airbag and on reversal extension of the airbag. The '546 design further lacks a means of dampening upon rebound travel of the suspension system (i.e., the extension action of the airbag), resulting in a rougher ride as this shock works in reverse—compressing as the shock gets longer and rebounding as it returns back to the shortened position. The system disclosed in the '546 patent is further limited in its range of motion and can be difficult to repair or replace.
Similarly, although the '960 patent discloses a suspension system that utilizes an airbag above the pivot point of the swingarm, it is designed for suspension systems where stock location of the dampener/shock absorber is also above the swingarm pivot point. Thus, such a system is not compatible with a SOFTAIL® type of suspension system. Further, the system of the '960 patent it fails to provide proper dampening through the use of a dampener/shock absorber in the stock or factory position on the motorcycle. This system is limited in its use and ease of adaptability to factory or stock bikes, because it requires complete removal and rebuilding of the shock dampener/shock absorber system. Accordingly, the '960 patent fails to provide an airbag system that provides ride comfort and ride height adjustability, that can be easily adapted to a SOFTAIL® type suspension.
The instant invention satisfies a need in the field of motorcycling by providing an airbag suspension system that can be fitted to motorcycles with a swingarm type rear suspension and that provides conventional compression and extension airbag action, combined with dampening action by a shock absorber located in the conventional SOFTAIL® shock absorber location, and while providing or preserving the comparatively concealed appearance of the suspension system desired in such SOFTAIL®type motorcycle frames. In addition, a preferred embodiment of the present invention discloses an arrangement that provides the dampening and shock absorbance function while permitting the adjustment of the ride height and/or the suspension movement.